Reconstruction and electrochemical oxidation of Au(110) surface in 0.1 M H2SO4

Variations of the surface structure and composition of the Au(110) electrode during the formation/lifting of the surface reconstruction and during the surface oxidation/reduction in 0.1 M aqueous sulfuric acid were studied by cyclic voltammetry, scanning tunneling microscopy and shell-isolated nanoparticle enhanced Raman spectroscopy. Annealing of the Au(110) electrode leads to a thermally-induced reconstruction formed by intermixed (1×3) and (1×2) phases. In a 0.1 M H2SO4 solution, the decrease of the potential of the atomically smooth Au(110)-(1×1) surface leads to the formation of a range of structures with increasing surface corrugation. The electrochemical oxidation of the Au(110) surface starts by the formation of anisotropic atomic rows of gold oxide. At higher potentials we observed a disordered structure of the surface gold oxide, similar to the one found for the Au(111) surface.

Regulating a Benzodifuran Single Molecule Redox Switch via Electrochemical Gating and Optimization of Molecule/Electrode Coupling

We report a novel strategy for the regulation of charge transport through single molecule junctions via the combination of external stimuli of electrode potential, internal modulation of molecular structures, and optimization of anchoring groups. We have designed redox-active benzodifuran (BDF) compounds as functional electronic units to fabricate metal–molecule–metal (m–M–m) junction devices by scanning tunneling microscopy (STM) and mechanically controllable break junctions (MCBJ). The conductance of thiol-terminated BDF can be tuned by changing the electrode potentials showing clearly an off/on/off single molecule redox switching effect. To optimize the response, a BDF molecule tailored with carbodithioate (−CS2–) anchoring groups was synthesized. Our studies show that replacement of thiol by carbodithioate not only enhances the junction conductance but also substantially improves the switching effect by enhancing the on/off ratio from 2.5 to 8.

Highly-effective gating of single-molecule junctions: an electrochemical approach

We report an electrochemical gating approach with [similar]100% efficiency to tune the conductance of single-molecule 4,4′-bipyridine junctions using scanning-tunnelling-microscopy break junction technique. Density functional theory calculation suggests that electrochemical gating aligns molecular frontier orbitals relative to the electrode Fermi-level, switching the molecule from an off resonance state to “partial” resonance.

Electrochemical control of a non-covalent binding between ferrocene and beta-cyclodextrin

The forces required for the detachment of ferrocene (Fc) from β-cyclodextrin (βCD) in a single host (βCD)–guest (Fc) complex were investigated using force spectroscopy under electrochemical conditions. The redox state of the guest Fc moiety as well as the structure of the supporting matrix was found to decisively affect the nanomechanical properties of the complex.

An immunoassay for the detection of circulating antigens in human echinococcosis.

An immunoassay (double-antibody-sandwich-ELISA) was developed to detect circulating antigens (CAg) in patients with cystic (Echinococcus granulosus) echinococcosis. Echinococcus antigens derived from heterologous intermediate hosts were used to immunize rabbits and to purify the rabbit-IgG-fraction obtained by affinity-chromatography, thus avoiding major interference with host components. The purified rabbit anti-hydatid IgG was immunosorbed with bovine and human sera. One part of the resulting IgG served as coating agent in a double antibody sandwich-ELISA; the other part, coupled to alkaline phosphatase, as detecting conjugate. The specificity of the antibody reaction was demonstrated by immunoelectrophoresis. Sera of 21 patients with cystic echinococcosis were examined with this test system. In seven of the patients' sera CAg were detected in concentrations ranging between 310 ng and 680 ng protein per ml serum. Comparing pre- and postoperative serum samples obtained from nine patients operated on for cystic echinococcosis, four sera were found to be CAg-positive before and three after operation.

Novel unsymmetrically functionalized BEDT–TTF derivatives: synthesis, crystal structure and electrochemical characterization

Novel functionalized bis(ethylenedithio)tetrathiafulvalene (BEDT–TTF) derivatives 4 and 5 have been synthesized in good yields from cyano precursor via a cross-coupling reaction. Their redox potentials have been studied by cyclic voltammetry in a dichloromethane solution; this indicated that they are slightly weaker electron donors than BEDT–TTF. Compound 4 has been studied by X–ray crystallography; this revealed that, in the crystal, the molecules were held together by some unconventional C–H···N and C–H···S hydrogen bonds.

Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond

Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge–discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g−1 at a current density of 10 μA cm−2 and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications.

Electrochemical CO2 Reduction - A Critical View on Fundamentals, Materials and Applications

The electrochemical reduction of CO2 has been extensively studied over the past decades. Nevertheless, this topic has been tackled so far only by using a very fundamental approach and mostly by trying to improve kinetics and selectivities toward specific products in half-cell configurations and liquid-based electrolytes. The main drawback of this approach is that, due to the low solubility of CO2 in water, the maximum CO2 reduction current which could be drawn falls in the range of 0.01–0.02 A cm–2. This is at least an order of magnitude lower current density than the requirement to make CO2-electrolysis a technically and economically feasible option for transformation of CO2 into chemical feedstock or fuel thereby closing the CO2 cycle. This work attempts to give a short overview on the status of electrochemical CO2 reduction with respect to challenges at the electrolysis cell as well as at the catalyst level. We will critically discuss possible pathways to increase both operating current density and conversion efficiency in order to close the gap with established energy conversion technologies.

Decreasing Proportion of Recent Infections among Newly Diagnosed HIV-1 Cases in Switzerland, 2008 to 2013 Based on Line-Immunoassay-Based Algorithms.

BACKGROUND: HIV surveillance requires monitoring of new HIV diagnoses and differentiation of incident and older infections. In 2008, Switzerland implemented a system for monitoring incident HIV infections based on the results of a line immunoassay (Inno-Lia) mandatorily conducted for HIV confirmation and type differentiation (HIV-1, HIV-2) of all newly diagnosed patients. Based on this system, we assessed the proportion of incident HIV infection among newly diagnosed cases in Switzerland during 2008-2013. METHODS AND RESULTS: Inno-Lia antibody reaction patterns recorded in anonymous HIV notifications to the federal health authority were classified by 10 published algorithms into incident (up to 12 months) or older infections. Utilizing these data, annual incident infection estimates were obtained in two ways, (i) based on the diagnostic performance of the algorithms and utilizing the relationship 'incident = true incident + false incident', (ii) based on the window-periods of the algorithms and utilizing the relationship 'Prevalence = Incidence x Duration'. From 2008-2013, 3'851 HIV notifications were received. Adult HIV-1 infections amounted to 3'809 cases, and 3'636 of them (95.5%) contained Inno-Lia data. Incident infection totals calculated were similar for the performance- and window-based methods, amounting on average to 1'755 (95% confidence interval, 1588-1923) and 1'790 cases (95% CI, 1679-1900), respectively. More than half of these were among men who had sex with men. Both methods showed a continuous decline of annual incident infections 2008-2013, totaling -59.5% and -50.2%, respectively. The decline of incident infections continued even in 2012, when a 15% increase in HIV notifications had been observed. This increase was entirely due to older infections. Overall declines 2008-2013 were of similar extent among the major transmission groups. CONCLUSIONS: Inno-Lia based incident HIV-1 infection surveillance proved useful and reliable. It represents a free, additional public health benefit of the use of this relatively costly test for HIV confirmation and type differentiation.

Low-cost disposable ALT electrochemical microsensors for in-vitro hepatotoxic assessment

Liver-on-chip systems are widely seen as having the potential to replace animal testing for long-term liver toxicity assessments. However, such systems necessitate solutions, such as electrochemical microsensors, to provide information about the cells exposed to chemical compounds in a confined space. This study describes the development of microsensors for the detection of alanine-aminotransferase (ALT), an intracellular enzyme found in hepatocytes, for monitoring the viability of in-vitro hepatic cell cultures. The electrochemical sensors were developed by using screen printed electrodes functionalized by drop-casting. These technologies are intended to produce disposable and low-cost sensors that can easily be exchanged once their performance is degraded. The sensors are capable of measuring ALT in a microfluidic environment through the detection of changes in glutamate concentration. The microsensors were found to be stable for more than 60 days and were successfully tested using hepatocellular lysates to assess their capability to quantify ALT activity in a hepatic cell culture. These results open the way to their integration in liver bioreactors to assess hepatocellular toxicity in-vitro.